"He used the compiler's self-compilation speed as a measure of the compiler's quality. Considering that Wirth's compilers were written in the languages they compiled, and that compilers are substantial and non-trivial pieces of software in their own right, this introduced a highly practical benchmarks that directly contested a compiler's complexity against its performance."

p44 "Oberon — The Overlooked Jewel" Michael Franz, in "The School of Niklaus Wirth".

https://www.google.com/books/edition/The_School_of_Niklaus_W...